Method for transmitting a scheduling request in a wireless communication system and a device therefor

ABSTRACT

The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for transmitting a scheduling request in a wireless communication system, the method comprising: receiving mapping information of SR resource sets and logical channels from an eNB, wherein one of the SR resource sets is a set of uplink resources that is used for transmitting SR; triggering a SR by a data of a logical channel; and transmitting the triggered SR on the SR resource set associated with the logical channel based on the mapping information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to International Application No. PCT/KR2017/001707 filed Feb. 16, 2017, which claims the benefit of U.S. Provisional Application No. 62/302,178 filed Mar. 2, 2016, the contents of which are incorporated herein in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system and, more particularly, to a method for transmitting a scheduling request in a wireless communication system and a device therefor.

BACKGROUND ART

As an example of a mobile communication system to which the present invention is applicable, a 3rd Generation Partnership Project Long Term Evolution (hereinafter, referred to as LTE) communication system is described in brief.

FIG. 1 is a view schematically illustrating a network structure of an E-UMTS as an exemplary radio communication system. An Evolved Universal Mobile Telecommunications System (E-UMTS) is an advanced version of a conventional Universal Mobile Telecommunications System (UMTS) and basic standardization thereof is currently underway in the 3GPP. E-UMTS may be generally referred to as a Long Term Evolution (LTE) system. For details of the technical specifications of the UMTS and E-UMTS, reference can be made to Release 7 and Release 8 of “3rd Generation Partnership Project; Technical Specification Group Radio Access Network”.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE), eNode Bs (eNBs), and an Access Gateway (AG) which is located at an end of the network (E-UTRAN) and connected to an external network. The eNBs may simultaneously transmit multiple data streams for a broadcast service, a multicast service, and/or a unicast service.

One or more cells may exist per eNB. The cell is set to operate in one of bandwidths such as 1.25, 2.5, 5, 10, 15, and 20 MHz and provides a downlink (DL) or uplink (UL) transmission service to a plurality of UEs in the bandwidth. Different cells may be set to provide different bandwidths. The eNB controls data transmission or reception to and from a plurality of UEs. The eNB transmits DL scheduling information of DL data to a corresponding UE so as to inform the UE of a time/frequency domain in which the DL data is supposed to be transmitted, coding, a data size, and hybrid automatic repeat and request (HARQ)-related information. In addition, the eNB transmits UL scheduling information of UL data to a corresponding UE so as to inform the UE of a time/frequency domain which may be used by the UE, coding, a data size, and HARQ-related information. An interface for transmitting user traffic or control traffic may be used between eNBs. A core network (CN) may include the AG and a network node or the like for user registration of UEs. The AG manages the mobility of a UE on a tracking area (TA) basis. One TA includes a plurality of cells.

Although wireless communication technology has been developed to LTE based on wideband code division multiple access (WCDMA), the demands and expectations of users and service providers are on the rise. In addition, considering other radio access technologies under development, new technological evolution is required to secure high competitiveness in the future. Decrease in cost per bit, increase in service availability, flexible use of frequency bands, a simplified structure, an open interface, appropriate power consumption of UEs, and the like are required.

DISCLOSURE Technical Problem

An object of the present invention devised to solve the problem lies in a method and device for transmitting a scheduling request in a wireless communication system. The technical problems solved by the present invention are not limited to the above technical problems and those skilled in the art may understand other technical problems from the following description.

Technical Solution

The object of the present invention can be achieved by providing a method for User Equipment (UE) operating in a wireless communication system as set forth in the appended claims.

In another aspect of the present invention, provided herein is a communication apparatus as set forth in the appended claims.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

Advantageous Effects

It is invented that the eNB configures SR resources on multiple cells and maps each SR resource to at least one certain logical channel. When the UE triggers an SR, the UE selects one of the SR resources based on the logical channel from which data triggers a Buffer Status Reporting (BSR).

It will be appreciated by persons skilled in the art that the effects achieved by the present invention are not limited to what has been particularly described hereinabove and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention.

FIG. 1 is a diagram showing a network structure of an Evolved Universal Mobile Telecommunications System (E-UMTS) as an example of a wireless communication system;

FIG. 2A is a block diagram illustrating network structure of an evolved universal mobile telecommunication system (E-UMTS), and FIG. 2B is a block diagram depicting architecture of a typical E-UTRAN and a typical EPC;

FIG. 3 is a diagram showing a control plane and a user plane of a radio interface protocol between a UE and an E-UTRAN based on a 3rd generation partnership project (3GPP) radio access network standard;

FIG. 4 is a view showing an example of a physical channel structure used in an E-UMTS system;

FIG. 5 is a block diagram of a communication apparatus according to an embodiment of the present invention;

FIG. 6 illustrates an example of CCs and CA in the LTE-A system, which are used in embodiments of the present disclosure;

FIG. 7 is a diagram for MAC structure overview in a UE side;

FIG. 8 is a diagram for Scheduling-request transmission;

FIG. 9 is a diagram for signaling of buffer status and power-headroom reports; and

FIG. 10 is conceptual diagram for transmitting a scheduling request according to an exemplary embodiment of the present invention.

BEST MODE

Universal mobile telecommunications system (UMTS) is a 3rd Generation (3G) asynchronous mobile communication system operating in wideband code division multiple access (WCDMA) based on European systems, global system for mobile communications (GSM) and general packet radio services (GPRS). The long-term evolution (LTE) of UMTS is under discussion by the 3rd generation partnership project (3GPP) that standardized UMTS.

The 3GPP LTE is a technology for enabling high-speed packet communications. Many schemes have been proposed for the LTE objective including those that aim to reduce user and provider costs, improve service quality, and expand and improve coverage and system capacity. The 3G LTE requires reduced cost per bit, increased service availability, flexible use of a frequency band, a simple structure, an open interface, and adequate power consumption of a terminal as an upper-level requirement.

Hereinafter, structures, operations, and other features of the present invention will be readily understood from the embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Embodiments described later are examples in which technical features of the present invention are applied to a 3GPP system.

Although the embodiments of the present invention are described using a long term evolution (LTE) system and a LTE-advanced (LTE-A) system in the present specification, they are purely exemplary. Therefore, the embodiments of the present invention are applicable to any other communication system corresponding to the above definition. In addition, although the embodiments of the present invention are described based on a frequency division duplex (FDD) scheme in the present specification, the embodiments of the present invention may be easily modified and applied to a half-duplex FDD (H-FDD) scheme or a time division duplex (TDD) scheme.

FIG. 2A is a block diagram illustrating network structure of an evolved universal mobile telecommunication system (E-UMTS). The E-UMTS may be also referred to as an LTE system. The communication network is widely deployed to provide a variety of communication services such as voice (VoIP) through IMS and packet data.

As illustrated in FIG. 2A, the E-UMTS network includes an evolved UMTS terrestrial radio access network (E-UTRAN), an Evolved Packet Core (EPC) and one or more user equipment. The E-UTRAN may include one or more evolved NodeB (eNodeB) 20, and a plurality of user equipment (UE) 10 may be located in one cell. One or more E-UTRAN mobility management entity (MME)/system architecture evolution (SAE) gateways 30 may be positioned at the end of the network and connected to an external network.

As used herein, “downlink” refers to communication from eNodeB 20 to UE 10, and “uplink” refers to communication from the UE to an eNodeB. UE 10 refers to communication equipment carried by a user and may be also referred to as a mobile station (MS), a user terminal (UT), a subscriber station (SS) or a wireless device.

FIG. 2B is a block diagram depicting architecture of a typical E-UTRAN and a typical EPC.

As illustrated in FIG. 2B, an eNodeB 20 provides end points of a user plane and a control plane to the UE 10. MME/SAE gateway 30 provides an end point of a session and mobility management function for UE 10. The eNodeB and MME/SAE gateway may be connected via an S1 interface.

The eNodeB 20 is generally a fixed station that communicates with a UE 10, and may also be referred to as a base station (BS) or an access point. One eNodeB 20 may be deployed per cell. An interface for transmitting user traffic or control traffic may be used between eNodeBs 20.

The MME provides various functions including NAS signaling to eNodeBs 20, NAS signaling security, AS Security control, Inter CN node signaling for mobility between 3GPP access networks, Idle mode UE Reachability (including control and execution of paging retransmission), Tracking Area list management (for UE in idle and active mode), PDN GW and Serving GW selection, MME selection for handovers with MME change, SGSN selection for handovers to 2G or 3G 3GPP access networks, Roaming, Authentication, Bearer management functions including dedicated bearer establishment, Support for PWS (which includes ETWS and CMAS) message transmission. The SAE gateway host provides assorted functions including Per-user based packet filtering (by e.g. deep packet inspection), Lawful Interception, UE IP address allocation, Transport level packet marking in the downlink, UL and DL service level charging, gating and rate enforcement, DL rate enforcement based on APN-AMBR. For clarity MME/SAE gateway 30 will be referred to herein simply as a “gateway,” but it is understood that this entity includes both an MME and an SAE gateway.

A plurality of nodes may be connected between eNodeB 20 and gateway 30 via the S1 interface. The eNodeBs 20 may be connected to each other via an X2 interface and neighboring eNodeBs may have a meshed network structure that has the X2 interface.

As illustrated, eNodeB 20 may perform functions of selection for gateway 30, routing toward the gateway during a Radio Resource Control (RRC) activation, scheduling and transmitting of paging messages, scheduling and transmitting of Broadcast Channel (BCCH) information, dynamic allocation of resources to UEs 10 in both uplink and downlink, configuration and provisioning of eNodeB measurements, radio bearer control, radio admission control (RAC), and connection mobility control in LTE ACTIVE state. In the EPC, and as noted above, gateway 30 may perform functions of paging origination, LTE-IDLE state management, ciphering of the user plane, System Architecture Evolution (SAE) bearer control, and ciphering and integrity protection of Non-Access Stratum (NAS) signaling.

The EPC includes a mobility management entity (MME), a serving-gateway (S-GW), and a packet data network-gateway (PDN-GW). The MME has information about connections and capabilities of UEs, mainly for use in managing the mobility of the UEs. The S-GW is a gateway having the E-UTRAN as an end point, and the PDN-GW is a gateway having a packet data network (PDN) as an end point.

FIG. 3 is a diagram showing a control plane and a user plane of a radio interface protocol between a UE and an E-UTRAN based on a 3GPP radio access network standard. The control plane refers to a path used for transmitting control messages used for managing a call between the UE and the E-UTRAN. The user plane refers to a path used for transmitting data generated in an application layer, e.g., voice data or Internet packet data.

A physical (PHY) layer of a first layer provides an information transfer service to a higher layer using a physical channel. The PHY layer is connected to a medium access control (MAC) layer located on the higher layer via a transport channel. Data is transported between the MAC layer and the PHY layer via the transport channel. Data is transported between a physical layer of a transmitting side and a physical layer of a receiving side via physical channels. The physical channels use time and frequency as radio resources. In detail, the physical channel is modulated using an orthogonal frequency division multiple access (OFDMA) scheme in downlink and is modulated using a single carrier frequency division multiple access (SC-FDMA) scheme in uplink.

The MAC layer of a second layer provides a service to a radio link control (RLC) layer of a higher layer via a logical channel. The RLC layer of the second layer supports reliable data transmission. A function of the RLC layer may be implemented by a functional block of the MAC layer. A packet data convergence protocol (PDCP) layer of the second layer performs a header compression function to reduce unnecessary control information for efficient transmission of an Internet protocol (IP) packet such as an IP version 4 (IPv4) packet or an IP version 6 (IPv6) packet in a radio interface having a relatively small bandwidth.

A radio resource control (RRC) layer located at the bottom of a third layer is defined only in the control plane. The RRC layer controls logical channels, transport channels, and physical channels in relation to configuration, re-configuration, and release of radio bearers (RBs). An RB refers to a service that the second layer provides for data transmission between the UE and the E-UTRAN. To this end, the RRC layer of the UE and the RRC layer of the E-UTRAN exchange RRC messages with each other.

One cell of the eNB is set to operate in one of bandwidths such as 1.25, 2.5, 5, 10, 15, and 20 MHz and provides a downlink or uplink transmission service to a plurality of UEs in the bandwidth. Different cells may be set to provide different bandwidths.

Downlink transport channels for transmission of data from the E-UTRAN to the UE include a broadcast channel (BCH) for transmission of system information, a paging channel (PCH) for transmission of paging messages, and a downlink shared channel (SCH) for transmission of user traffic or control messages. Traffic or control messages of a downlink multicast or broadcast service may be transmitted through the downlink SCH and may also be transmitted through a separate downlink multicast channel (MCH).

Uplink transport channels for transmission of data from the UE to the E-UTRAN include a random access channel (RACH) for transmission of initial control messages and an uplink SCH for transmission of user traffic or control messages. Logical channels that are defined above the transport channels and mapped to the transport channels include a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), and a multicast traffic channel (MTCH).

FIG. 4 is a view showing an example of a physical channel structure used in an E-UMTS system. A physical channel includes several subframes on a time axis and several subcarriers on a frequency axis. Here, one subframe includes a plurality of symbols on the time axis. One subframe includes a plurality of resource blocks and one resource block includes a plurality of symbols and a plurality of subcarriers. In addition, each subframe may use certain subcarriers of certain symbols (e.g., a first symbol) of a subframe for a physical downlink control channel (PDCCH), that is, an L1/L2 control channel. In FIG. 4, an L1/L2 control information transmission area (PDCCH) and a data area (PDSCH) are shown. In one embodiment, a radio frame of 10 ms is used and one radio frame includes 10 subframes. In addition, one subframe includes two consecutive slots. The length of one slot may be 0.5 ms. In addition, one subframe includes a plurality of OFDM symbols and a portion (e.g., a first symbol) of the plurality of OFDM symbols may be used for transmitting the L1/L2 control information. A transmission time interval (TTI) which is a unit time for transmitting data is 1 ms.

A base station and a UE mostly transmit/receive data via a PDSCH, which is a physical channel, using a DL-SCH which is a transmission channel, except a certain control signal or certain service data. Information indicating to which UE (one or a plurality of UEs) PDSCH data is transmitted and how the UE receive and decode PDSCH data is transmitted in a state of being included in the PDCCH.

For example, in one embodiment, a certain PDCCH is CRC-masked with a radio network temporary identity (RNTI) “A” and information about data is transmitted using a radio resource “B” (e.g., a frequency location) and transmission format information “C” (e.g., a transmission block size, modulation, coding information or the like) via a certain subframe. Then, one or more UEs located in a cell monitor the PDCCH using its RNTI information. And, a specific UE with RNTI “A” reads the PDCCH and then receive the PDSCH indicated by B and C in the PDCCH information.

FIG. 5 is a block diagram of a communication apparatus according to an embodiment of the present invention.

The apparatus shown in FIG. 5 can be a user equipment (UE) and/or eNB adapted to perform the above mechanism, but it can be any apparatus for performing the same operation.

As shown in FIG. 5, the apparatus may comprises a DSP/microprocessor (110) and RF module (transmiceiver; 135). The DSP/microprocessor (110) is electrically connected with the transciver (135) and controls it. The apparatus may further include power management module (105), battery (155), display (115), keypad (120), SIM card (125), memory device (130), speaker (145) and input device (150), based on its implementation and designer's choice.

Specifically, FIG. 5 may represent a UE comprising a receiver (135) configured to receive a request message from a network, and a transmitter (135) configured to transmit the transmission or reception timing information to the network. These receiver and the transmitter can constitute the transceiver (135). The UE further comprises a processor (110) connected to the transceiver (135: receiver and transmitter).

Also, FIG. 5 may represent a network apparatus comprising a transmitter (135) configured to transmit a request message to a UE and a receiver (135) configured to receive the transmission or reception timing information from the UE. These transmitter and receiver may constitute the transceiver (135). The network further comprises a processor (110) connected to the transmitter and the receiver. This processor (110) may be configured to calculate latency based on the transmission or reception timing information.

FIG. 6 illustrates an example of CCs and CA in the LTE-A system, which are used in embodiments of the present disclosure.

A 3GPP LTE system (hereinafter, referred to as an LTE system) uses Multi-Carrier Modulation (MCM) in which a single Component Carrier (CC) is divided into a plurality of bands. In contrast, a 3GPP LTE-A system (hereinafter, referred to an LTE-A system) may use CA by aggregating one or more CCs to support a broader system bandwidth than the LTE system. The term CA is interchangeably used with carrier combining, multi-CC environment, or multi-carrier environment.

In the present disclosure, multi-carrier means CA (or carrier combining). Herein, CA covers aggregation of contiguous carriers and aggregation of non-contiguous carriers. The number of aggregated CCs may be different for a DL and a UL. If the number of DL CCs is equal to the number of UL CCs, this is called symmetric aggregation. If the number of DL CCs is different from the number of UL CCs, this is called asymmetric aggregation. The term CA is interchangeable with carrier combining, bandwidth aggregation, spectrum aggregation, etc.

The LTE-A system aims to support a bandwidth of up to 100 MHz by aggregating two or more CCs, that is, by CA. To guarantee backward compatibility with a legacy IMT system, each of one or more carriers, which has a smaller bandwidth than a target bandwidth, may be limited to a bandwidth used in the legacy system.

For example, the legacy 3GPP LTE system supports bandwidths {1.4, 3, 5, 10, 15, and 20 MHz} and the 3GPP LTE-A system may support a broader bandwidth than 20 MHz using these LTE bandwidths. A CA system of the present disclosure may support CA by defining a new bandwidth irrespective of the bandwidths used in the legacy system.

There are two types of CA, intra-band CA and inter-band CA. Intra-band CA means that a plurality of DL CCs and/or UL CCs are successive or adjacent in frequency. In other words, the carrier frequencies of the DL CCs and/or UL CCs are positioned in the same band. On the other hand, an environment where CCs are far away from each other in frequency may be called inter-band CA. In other words, the carrier frequencies of a plurality of DL CCs and/or UL CCs are positioned in different bands. In this case, a UE may use a plurality of Radio Frequency (RF) ends to conduct communication in a CA environment.

The LTE-A system adopts the concept of cell to manage radio resources. The above-described CA environment may be referred to as a multi-cell environment. A cell is defined as a pair of DL and UL CCs, although the UL resources are not mandatory. Accordingly, a cell may be configured with DL resources alone or DL and UL resources.

For example, if one serving cell is configured for a specific UE, the UE may have one DL CC and one UL CC. If two or more serving cells are configured for the UE, the UE may have as many DL CCs as the number of the serving cells and as many UL CCs as or fewer UL CCs than the number of the serving cells, or vice versa. That is, if a plurality of serving cells are configured for the UE, a CA environment using more UL CCs than DL CCs may also be supported.

CA may be regarded as aggregation of two or more cells having different carrier frequencies (center frequencies). Herein, the term ‘cell’ should be distinguished from ‘cell’ as a geographical area covered by an eNB. Hereinafter, intra-band CA is referred to as intra-band multi-cell and inter-band CA is referred to as inter-band multi-cell.

FIG. 6(a) illustrates a single carrier structure in the LTE system. There are a DL CC and a UL CC and one CC may have a frequency range of 20 MHz.

FIG. 6(b) illustrates a CA structure in the LTE-A system. In the illustrated case of FIG. 6(b), three CCs each having 20 MHz are aggregated. While three DL CCs and three UL CCs are configured, the numbers of DL CCs and UL CCs are not limited. In CA, a UE may monitor three CCs simultaneously, receive a DL signal/DL data in the three CCs, and transmit a UL signal/UL data in the three CCs.

FIG. 7 is a diagram for MAC structure overview in a UE side.

The MAC layer handles logical-channel multiplexing, hybrid-ARQ retransmissions, and uplink and downlink scheduling. It is also responsible for multiplexing/demultiplexing data across multiple component carriers when carrier aggregation is used.

The MAC provides services to the RLC in the form of logical channels. A logical channel is defined by the type of information it carries and is generally classified as a control channel, used for transmission of control and configuration information necessary for operating an LTE system, or as a traffic channel, used for the user data. The set of logical channel types specified for LTE includes Broadcast Control Channel (BCCH), Paging Control Channel (PCCH), Common Control Channel (CCCH), Dedicated Control Channel (DCCH), Multicast Control Channel (MCCH), Dedicated Traffic Channel (DTCH), Multicast Traffic Channel (MTCH).

From the physical layer, the MAC layer uses services in the form of transport channels. A transport channel is defined by how and with what characteristics the information is transmitted over the radio interface. Data on a transport channel is organized into transport blocks. In each Transmission Time Interval (TTI), at most one transport block of dynamic size is transmitted over the radio interface to/from a terminal in the absence of spatial multiplexing. In the case of spatial multiplexing (MIMO), there can be up to two transport blocks per TTI.

Associated with each transport block is a Transport Format (TF), specifying how the transport block is to be transmitted over the radio interface. The transport format includes information about the transport-block size, the modulation-and-coding scheme, and the antenna mapping. By varying the transport format, the MAC layer can thus realize different data rates. Rate control is therefore also known as transport-format selection.

To support priority handling, multiple logical channels, where each logical channel has its own RLC entity, can be multiplexed into one transport channel by the MAC layer. At the receiver, the MAC layer handles the corresponding demultiplexing and forwards the RLC PDUs to their respective RLC entity for in-sequence delivery and the other functions handled by the RLC. To support the demultiplexing at the receiver, a MAC is used. To each RLC PDU, there is an associated sub-header in the MAC header. The sub-header contains the identity of the logical channel (LCID) from which the RLC PDU originated and the length of the PDU in bytes. There is also a flag indicating whether this is the last sub-header or not. One or several RLC PDUs, together with the MAC header and, if necessary, padding to meet the scheduled transport-block size, form one transport block which is forwarded to the physical layer.

In addition to multiplexing of different logical channels, the MAC layer can also insert the so-called MAC control elements into the transport blocks to be transmitted over the transport channels. A MAC control element is used for inband control signaling—for example, timing-advance commands and random-access response. Control elements are identified with reserved values in the LCID field, where the LCID value indicates the type of control information.

Furthermore, the length field in the sub-header is removed for control elements with a fixed length.

The MAC multiplexing functionality is also responsible for handling of multiple component carriers in the case of carrier aggregation. The basic principle for carrier aggregation is independent processing of the component carriers in the physical layer, including control signaling, scheduling and hybrid-ARQ retransmissions, while carrier aggregation is invisible to RLC and PDCP. Carrier aggregation is therefore mainly seen in the MAC layer, where logical channels, including any MAC control elements, are multiplexed to form one (two in the case of spatial multiplexing) transport block(s) per component carrier with each component carrier having its own hybrid-ARQ entity.

When logical channels are configured by the eNB via RRC signaling, the information of logical channel configuration (i.e. IE LogicalChannelConfig) is used to configure the logical channel parameters.

The information of logical channel configuration includes following Table 1.

TABLE 1  -- ASN1STATR LogicalChannelConfig : := SEQUENCE {   ul-SpecificParameters SEQUENCE {     priority INTEGER (1..16),     prioritisedBitRate ENUMERATED { kBps0, kBps8, kBps16, kBps32 kBps64, kBps128, kBps256, infinity, kBps512-v1020, kBps1024-v1020, kBps2048-v1020, spare 5, spare 4, spare 3, spare 2, spare1}     bucketSizeDuration ENUMERATED { ms50, ms100, ms150, ms300, ms500, ms1000, spare2,     logicalChannelGroup spare1},       OPTIONAL, INTEGER (0..3) OPTIONAL --Need OR -- Cond UL    }    ...,   [[ logicalChannelSR-Mask-r9 ENUMERATED {setup} OPTIONAL -- Cond SRmask   ]],   [[ logicalChannelSR-Prohibit-r12 BOOLEAN OPTIONAL --Need ON   ]] }  -- ASN1STOP

Priority means logical channel priority, and prioritisedBitRate means Prioritized Bit Rate for logical channel prioritization.

logicalChannelGroup means mapping of logical channel to logical channel group for BSR reporting.

logicalChannelSR-Mask means controlling SR triggering on a logical channel basis when an uplink grant is configured, and a value of TRUE of the logicalChannelSR-Prohibit indicates that the logicalChannelSR-ProhibitTimer is enabled for the logical channel. E-UTRAN only (optionally) configures the field (i.e. indicates value TRUE) if logicalChannelSR-ProhibitTimer is configured.

FIG. 10 is a diagram for Scheduling Request transmission.

The scheduler needs knowledge about the amount of data awaiting transmission from the terminals to assign the proper amount of uplink resources. Obviously, there is no need to provide uplink resources to a terminal with no data to transmit as this would only result in the terminal performing padding to fill up the granted resources. Hence, as a minimum, the scheduler needs to know whether the terminal has data to transmit and should be given a grant. This is known as a scheduling request.

A scheduling request is a simple flag, raised by the terminal to request uplink resources from the uplink scheduler. Since the terminal requesting resources by definition has no PUSCH resource, the scheduling request is transmitted on the PUCCH. Each terminal can be assigned a dedicated PUCCH scheduling request resource, occurring every nth subframe. With a dedicated scheduling-request mechanism, there is no need to provide the identity of the terminal requesting to be scheduled as the identity of the terminal is implicitly known from the resources upon which the request is transmitted.

When data with higher priority than already existing in the transmit buffers arrives at the terminal and the terminal has no grant and hence cannot transmit the data, the terminal transmits a scheduling request at the next possible instant, as illustrated in FIG. 10. Upon reception of the request, the scheduler can assign a grant to the terminal. If the terminal does not receive a scheduling grant until the next possible scheduling-request instant, then the scheduling request is repeated. There is only a single scheduling-request bit, irrespective of the number of uplink component carriers the terminal is capable of. In the case of carrier aggregation, the scheduling request is transmitted on the primary component carrier, in line with the general principle of PUCCH transmission on the primary component carrier only.

The use of a single bit for the scheduling request is motivated by the desire to keep the uplink overhead small, as a multi-bit scheduling request would come at a higher cost. A consequence of the single-bit scheduling request is the limited knowledge at the eNodeB about the buffer situation at the terminal when receiving such a request. Different scheduler implementations handle this differently. One possibility is to assign a small amount of resources to ensure that the terminal can exploit them efficiently without becoming power limited. Once the terminal has started to transmit on the UL-SCH, more detailed information about the buffer status and power headroom can be provided through the inband MAC control message, as discussed below. Knowledge of the service type may also be used—for example, in the case of voice the uplink resource to grant is preferably the size of a typical voice-over-IP package. The scheduler may also exploit, for example, path-loss measurements used for mobility and handover decisions to estimate the amount of resources the terminal may efficiently utilize.

An alternative to a dedicated scheduling-request mechanism would be a contention-based design. In such a design, multiple terminals share a common resource and provide their identity as part of the request. This is similar to the design of the random access.

The number of bits transmitted from a terminal as part of a request would in this case be larger, with the correspondingly larger need for resources. In contrast, the resources are shared by multiple users. Basically, contention-based designs are suitable for a situation where there are a large number of terminals in the cell and the traffic intensity, and hence the scheduling intensity, is low. In situations with higher intensities, the collision rate between different terminals simultaneously requesting resources would be too high and lead to an inefficient design.

Although the scheduling-request design for LTE relies on dedicated resources, a terminal that has not been allocated such resources obviously cannot transmit a scheduling request. Instead, terminals without scheduling-request resources configured rely on the random-access mechanism. In principle, an LTE terminal can therefore be configured to rely on a contention-based mechanism if this is advantageous in a specific deployment.

The Scheduling Request (SR) is used for requesting UL-SCH resources for new transmission. When an SR is triggered, it shall be considered as pending until it is cancelled. All pending SR(s) shall be cancelled and sr-ProhibitTimer shall be stopped when a MAC PDU is assembled and this PDU includes a BSR which contains buffer status up to (and including) the last event that triggered a BSR, or when the UL grant(s) can accommodate all pending data available for transmission.

If an SR is triggered and there is no other SR pending, the UE may set the SR_COUNTER to 0.

As long as one SR is pending, if no UL-SCH resources are available for a transmission in this TTI, the UE may initiate a Random Access procedure on a PCell and cancel all pending SRs if the UE has no valid PUCCH resource for SR configured in any TTI.

Else if the UE has a valid PUCCH resource for SR configured for this TTI and if this TTI is not part of a measurement gap and if sr-ProhibitTimer is not running, if SR_COUNTER<dsr-TransMax, the UE may increment SR_COUNTER by 1, instruct the physical layer to signal the SR on PUCCH, and start the sr-ProhibitTimer.

if SR_COUNTER≥dsr-TransMax, the UE may notify RRC to release PUCCH/SRS for all serving cells, clear any configured downlink assignments and uplink grants, and initiate a Random Access procedure on the PCell and cancel all pending SRs.

When SRs are configured by the eNB via RRC signaling, the information of SchedulingRequest configuration (i.e. SchedulingRequestConfig) is used to specify the Scheduling Request related parameters.

The information of logical channel configuration includes following Table 2.

TABLE 2  -- ASN1STATR SchedulingRequestConfig : := CHOICE {   release NULL,   setup SEQUENCE {     sr-PUCCH-ResourceIndex INTEGER (0..2047),     sr-ConfigIndex INTEGER (0..157),     dsr-TransMax ENUMERATED { n4, n8, n16, n32, n64, spare3, spare2, spare1}   } } SchedulingRequestConfig-v1020 : := SEQUENCE {   sr-PUCCH-ResourceIndexP1-r10 INTEGER (0..2047),    OPTIONAL   --Need OR } -- ASN1STOP

FIG. 11 is a diagram for signaling of buffer status and power-headroom reports.

Terminals that already have a valid grant obviously do not need to request uplink resources. However, to allow the scheduler to determine the amount of resources to grant to each terminal in future subframes, information about the buffer situation and the power availability is useful, as discussed above. This information is provided to the scheduler as part of the uplink transmission through MAC control element. The LCID field in one of the MAC subheaders is set to a reserved value indicating the presence of a buffer status report, as illustrated in FIG. 11.

From a scheduling perspective, buffer information for each logical channel is beneficial, although this could result in a significant overhead. Logical channels are therefore grouped into logical-channel groups and the reporting is done per group. The buffer-size field in a buffer-status report indicates the amount of data awaiting transmission across all logical channels in a logical-channel group.

The Buffer Status Reporting (BSR) procedure is used to provide a serving eNB with information about the amount of data available for transmission in the UL buffers of the UE. RRC may control BSR reporting by configuring the two timers periodicBSR-Timer and retxBSR-Timer and by, for each logical channel, optionally signalling Logical Channel Group which allocates the logical channel to an LCG (Logical Channel Group).

For the Buffer Status reporting procedure, the UE may consider all radio bearers which are not suspended and may consider radio bearers which are suspended. A Buffer Status Report (BSR) may be triggered if any of the following events occur: i) arrival of data with higher priority than currently in the transmission buffer—that is, data in a logical-channel group with higher priority than the one currently being transmitted—as this may impact the scheduling decision, (i.e., UL data, for a logical channel which belongs to a LCG, becomes available for transmission in the RLC entity or in the PDCP entity and either the data belongs to a logical channel with higher priority than the priorities of the logical channels which belong to any LCG and for which data is already available for transmission, or there is no data available for transmission for any of the logical channels which belong to a LCG, in which case the BSR is referred below to as “Regular BSR”; retxBSR-Timer expires and the UE has data available for transmission for any of the logical channels which belong to a LCG, in which case the BSR is referred below to as “Regular BSR”) ii) change of serving cell, in which case a buffer-status report is useful to provide the new serving cell with information about the situation in the terminal, iii) Periodically as controlled by a timer (i.e.,periodicBSR-Timer expires, in which case the BSR is referred below to as “Periodic BSR”), iv) instead of padding. If the amount of padding required to match the scheduled transport block size is larger than a buffer-status report, a buffer-status report is inserted. Clearly it is better to exploit the available payload for useful scheduling information instead of padding if possible (i.e., UL resources are allocated and number of padding bits is equal to or larger than the size of the Buffer Status Report MAC control element plus its subheader, in which case the BSR is referred below to as “Padding BSR”).

For Regular BSR, if the BSR is triggered due to data becoming available for transmission for a logical channel for which logicalChannelSR-ProhibitTimer is configured by upper layers, if not running, the MAC entity starts the logicalChannelSR-ProhibitTimer. Else, if running, the MAC entity stops the logicalChannelSR-ProhibitTimer.

For Regular and Periodic BSR, if more than one LCG has data available for transmission in the TTI where the BSR is transmitted, the UE may report Long BSR. If else, the UE may report Short BSR.

If the Buffer Status reporting procedure determines that at least one BSR has been triggered and not cancelled, if the UE has UL resources allocated for new transmission for this TTI, the UE may instruct the Multiplexing and Assembly procedure to generate the BSR MAC control element(s), start or restart periodicBSR-Timer except when all the generated BSRs are Truncated BSRs, and start or restart retxBSR-Timer.

Else if a Regular BSR has been triggered and logicalChannelSR-ProhibitTimer is not running, if an uplink grant is not configured or the Regular BSR was not triggered due to data becoming available for transmission for a logical channel for which logical channel SR masking (logicalChannelSR-Mask) is setup by upper layers, a Scheduling Request shall be triggered.

A MAC PDU may contain at most one MAC BSR control element, even when multiple events trigger a BSR by the time a BSR can be transmitted in which case the Regular BSR and the Periodic BSR shall have precedence over the padding BSR.

The MAC entity may restart retxBSR-Timer upon indication of a grant for transmission of new data on any UL-SCH.

All triggered BSRs may be cancelled in case UL grants in this subframe can accommodate all pending data available for transmission but is not sufficient to additionally accommodate the BSR MAC control element plus its subheader. All triggered BSRs shall be cancelled when a BSR is included in a MAC PDU for transmission.

The MAC entity shall transmit at most one Regular/Periodic BSR in a TTI. If the UE is requested to transmit multiple MAC PDUs in a TTI, it may include a padding BSR in any of the MAC PDUs which do not contain a Regular/Periodic BSR.

All BSRs transmitted in a TTI always reflect the buffer status after all MAC PDUs have been built for this TTI. Each LCG shall report at the most one buffer status value per TTI and this value shall be reported in all BSRs reporting buffer status for this LCG.

In supporting cell-specific operation for CA, it would be possible to map a certain application to a specific cell. It means that the data from a certain logical channel would only be transmitted on a cell which is mapped to the certain logical channel. For this, the eNB needs to provide an uplink grant for/on a specific cell by considering the data to be transmitted by using the uplink grant.

Currently, having one SR procedure, it is not possible to inform the eNB of logical channel from which data triggers BSR/SR. In other words, the UE has one common SR procedure, and data from any logical channel can trigger the SR procedure. Thus, when the eNB receives the SR, the eNB cannot know the logical channel that has data to be transmitted. Accordingly, the eNB has to receive additional information of, for example, logical channel that has data to transmit. This has been realized by BSR, i.e., the UE reports BSR per LCG, and the eNB can roughly know which logical channels have data to transmit. Then, the eNB can provide the uplink grant for/on a certain cell that is mapped to the logical channels.

The current behaviour would bring a delay in data transmission because the UE has to send the information of logical channel that has data, e.g., BSR, in order to get an uplink grant for/on the mapped cell.

FIG. 10 is conceptual diagram for transmitting a scheduling request according to an exemplary embodiment of the present invention.

It is invented that the UE selects an SR resource based on a logical channel from which data triggers BSR. For this, there is a mapping between SR resources and logical channels, which can be configured by an eNB. In detail, the eNB configures SR resources on multiple cells and maps each SR resources to at least one certain logical channel. When the UE triggers an SR, the UE selects one of the SR resources based on the logical channel from which data triggers a BSR.

A UE is configured with at least one set of SR resource by an eNB (S1001).

Preferably, an SR resource set refers to a set of uplink resources that can be used for transmitting a Scheduling Resource by the UE.

The UE receives the mapping information of SR resource set and logical channels (i.e., SR-LC mapping) from the eNB via RRC/PDCP/RLC/MAC/PHY signaling (S1003).

The mapping information of SR resource set and logical channels includes an SR resource set identity; or, a cell identity on which an SR resource set is configured, at least one Logical Channel Group (LCG) identity mapped to the SR resource set with the SR resource identity.

When the mapping information of SR resource sets and logical channels includes at least one SR resource set identity and at least one logical channel identity, each of the at least one SR resource set identity is associated with one or more logical channel identities, or each of the least one logical channel identity is associated with one or more SR resource set identities.

When the mapping information of SR resource sets and logical channels includes at least one SR resource set identity and at least one Logical Channel Group (LCG) identity, each of the at least one SR resource set identity is associated with one or more LCG identities, or each of the least one LCG identity is associated with one or more SR resource set identities.

When the UE receives the mapping information, the UE considers that a logical channel indicated by the logical channel identity or a logical channel belonging to the LCG indicated by the LCG identity is mapped to the SR resource set indicated by the SR resource identity or the SR resource set configured on the cell indicated by the cell identity.

When the UE triggers a Buffer Status Report (BSR) and SR by a data of a logical channel, the UE checks the logical channel from which data triggers BSR and SR (S1305).

According to the mapping information, the UE selects the SR resource set which is mapped to the logical channel from which data triggers BSR and SR (S1307).

If one of the SR resource sets is associated with at least one logical channel, because there is only one SR resource set associated with the logical channel from which data triggers BSR and SR, the UE doesn't need to select the SR resource set.

In case there are multiple SR resource sets which are mapped to the logical channel from which data triggers BSR and SR, the UE selects one SR resource set among the SR resource sets mapped to the logical channel, or the UE selects all SR resource sets mapped to the logical channel.

When the one of the one or more SR resource sets is selected, the UE selects the one SR resource set randomly, or the UE selects the one SR resource set of which SR transmission opportunity occurs earliest in time domain, or the UE selects the one SR resource set of a cell which has a best channel quality, or the UE selects the one SR resource set of a cell with which a least number of logical channels are associated.

The UE sends a Scheduling Request on the selected SR resource set (S1309).

If one of the SR resource sets is associated with at least one logical channel, the UE transmits the triggered SR on the SR resource set associated with the logical channel based on the mapping information.

In case there are multiple SR resource sets which are mapped to the logical channel from which data triggers BSR and SR, the UE sends the Scheduling Request on one SR resource set among the SR resource sets mapped to the logical channel, or on all SR resource sets mapped to the logical channel.

During the time there is any pending SR, if the UE triggers another BSR and SR by a data of a logical channel, and if the logical channel is different from the logical channel that is related to any pending SR, the UE selects the SR resource set which is mapped to the logical channel from which data triggers BSR and SR according to the SR-LC mapping, and the UE sends a Scheduling Request on the selected SR resource set.

The UE may count the number of SR transmissions on each SR resource set when the UE performs SR repetition transmission.

When the number of SR transmissions on one SR resource set reaches its maximum value, if there is any pending SR transmission other than the SR transmission reaching its maximum number of transmissions, the UE does not trigger a random access procedure and the UE does not cancel any pending SR.

When the number of SR transmissions on one SR resource set reaches its maximum value, if there is no other pending SR transmission other than the SR transmission reaching its maximum number of transmissions, the UE triggers a random access procedure, and UE cancel all pending SRs.

The embodiments of the present invention described hereinbelow are combinations of elements and features of the present invention. The elements or features may be considered selective unless otherwise mentioned. Each element or feature may be practiced without being combined with other elements or features. Further, an embodiment of the present invention may be constructed by combining parts of the elements and/or features. Operation orders described in embodiments of the present invention may be rearranged. Some constructions of any one embodiment may be included in another embodiment and may be replaced with corresponding constructions of another embodiment. It is obvious to those skilled in the art that claims that are not explicitly cited in each other in the appended claims may be presented in combination as an embodiment of the present invention or included as a new claim by subsequent amendment after the application is filed.

In the embodiments of the present invention, a specific operation described as performed by the BS may be performed by an upper node of the BS. Namely, it is apparent that, in a network comprised of a plurality of network nodes including a BS, various operations performed for communication with an MS may be performed by the BS, or network nodes other than the BS. The term ‘eNB’ may be replaced with the term ‘fixed station’, ‘Node B’, ‘Base Station (BS)’, ‘access point’, etc.

The above-described embodiments may be implemented by various means, for example, by hardware, firmware, software, or a combination thereof.

In a hardware configuration, the method according to the embodiments of the present invention may be implemented by one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers, microcontrollers, or microprocessors.

In a firmware or software configuration, the method according to the embodiments of the present invention may be implemented in the form of modules, procedures, functions, etc. performing the above-described functions or operations. Software code may be stored in a memory unit and executed by a processor. The memory unit may be located at the interior or exterior of the processor and may transmit and receive data to and from the processor via various known means.

Those skilled in the art will appreciate that the present invention may be carried out in other specific ways than those set forth herein without departing from essential characteristics of the present invention. The above embodiments are therefore to be construed in all aspects as illustrative and not restrictive. The scope of the invention should be determined by the appended claims, not by the above description, and all changes coming within the meaning of the appended claims are intended to be embraced therein.

INDUSTRIAL APPLICABILITY

While the above-described method has been described centering on an example applied to the 3GPP LTE system, the present invention is applicable to a variety of wireless communication systems in addition to the 3GPP LTE system. 

The invention claimed is:
 1. A method performed by a User Equipment (UE) operating in a wireless communication system, the method comprising: configuring at least two Scheduling Request (SR) resource sets; receiving, via Radio Resource Control (RRC) signaling from a Base Station (BS), identity information regarding a SR resource set among the at least two SR resource sets, wherein the SR resource set is mapped with a specific logical channel, wherein the SR resource set includes uplink resources for a SR; triggering the SR by data of the specific logical channel; and transmitting the triggered SR on one of the uplink resources based on the identity information, wherein the one of the uplink resources is selected by the UE.
 2. The method according to claim 1, wherein the SR resource set is related to one or more logical channels including the specific logical channel.
 3. The method according to claim 1, wherein the identity information is related to an identity of Logical Channel Group (LCG) including the specific logical channel.
 4. The method according to claim 1, wherein based on a number of SR transmissions on the SR resource set reaching a maximum value and based on any pending SR transmission other than the SR transmission reaching the maximum value, the UE does not trigger a random access procedure, and the UE does not cancel any pending SR.
 5. The method according to claim 1, wherein based on a number of SR transmissions on the SR resource set reaching a maximum value and based on no other pending SR transmission other than the SR transmission reaching the maximum value, the UE triggers a random access procedure, and the UE cancels all pending SRs.
 6. A User Equipment (UE) configured to operate in a wireless communication system, the UE comprising: a Radio Frequency (RF) module; and a processor operably coupled with the RF module and configured to: configure at least two Scheduling Request (SR) resource sets; receive, via Radio Resource Control (RRC) signaling from a Base Station (BS), identity information regarding a SR resource set among the at least two SR resource sets, wherein the SR resource set is mapped with a specific logical channel, wherein the SR resource set includes uplink resources for a SR; trigger the SR by data of the specific logical channel; and transmit the triggered SR on one of the uplink resources based on the identity information, wherein the one of the uplink resources is selected by the UE.
 7. The UE according to claim 6, wherein the SR resource set is related to one or more logical channels including the specific logical channel.
 8. The UE according to claim 6, wherein the identity information is related to an identity of Logical Channel Group (LCG) including the specific logical channel.
 9. The UE according to claim 6, wherein based on a number of SR transmissions on the SR resource set reaching a maximum value and based on any pending SR transmission other than the SR transmission reaching the maximum value, the processor does not trigger a random access procedure, and the processor does not cancel any pending SR.
 10. The UE according to claim 6, wherein based on a number of SR transmissions on the SR resource set reaching a maximum value and based on no other pending SR transmission other than the SR transmission reaching the maximum value, the processor triggers a random access procedure, and the processor cancels all pending SRs. 